Various forms of devices for lifting individual sheets from a stack are well known in the prior art. Generally, conventional devices may involve vacuum heads for lifting the top sheet from a stack as well as blower apparatus for improving selectivity. Additionally, conventional systems also employ structures that are sometimes referred to as "Cat's Whiskers" or retainers which contact the stack of paper at locations adjacent one edge and release the top sheet on a stack while retaining the second sheet. Conventionally, cat's whiskers or sheet retainers have taken the form of leaf spring devices which forcefully engage the stack of sheets, however, yield to release the top sheet from the stack. Although such structures operate effectively under ideal conditions, maintaining the desirable spring force is frequently a problem. Consequently, some substantial amount of time is expended in adjusting and replacing these sheet retainers. Accordingly, an improved retainer for use as a sheet separator was developed as disclosed in U.S. Pat. No. 3,403,903. However, a need continues for a simpler, more rugged mechanism.
In general, the present invention incorporates a retainer (cat's whisker) for use in combination with the components of a sheet delivery system, which retainer includes a bracket that may be affixed to the mechanism at a location contiguous to the stack from which sheets are delivered. The bracket defines an elongate chamber which contains a torsion spring with stationary anchored ends and which supports a tab to dwell in flat facing contact with the top sheet of the stack so as to yieldably release the sheet and immediately thereafter engage the next sheet, retaining it until the time of the next sheet delivery.
Systems incorporating retainers in accordance with the present invention may be economically manufactured and are capable of effective operation for extended periods with relatively little adjustment. As will be apparent from the complete presentation as set forth below, the retainers are capable of economical manufacture and simple installation.